The present invention relates to a method and apparatus for testing tightness of at least one hollow body and for detecting a change in volume caused by pressure stress applied to walls of the hollow body such as, for example, a flexible hollow body such as a coffee package.
In the packaging of certain foodstuffs such as sweeteners and coffee or also medications such as, for example, effervescent tablets, it is essential that the packaging containers are sealed tight against the environment in order to prevent the packaged goods from becoming contaminated by, for example, atmospheric humidity. The goods are sometimes packed in containers such as cans or pouches. These containers are generally dimensionally stable or flexible hollow bodies which are fitted with lids or closable sections which can be opened, but which in the closed state are intended to tightly seal the interior of the hollow body.
Various procedures, for example, welding, are used in the manufacture of such containers. In addition to the tightness of such hollow bodies, also the rigidity of the walls of the dimensionally stable containers, especially in the area of junction points, is an essential criteriion determining their useability. Excessively rigid or excessively weak sections such as weld seams, may result in cracks forming when the container is in use, for example, in areas where parts of different rigidity are joined.